1. Field of the Invention
The present invention relates to a pressure-controlling apparatus employed in a pre-chamber of a low-atmospheric pressure environmental testing chamber for conducting various durability tests of a self-propelled vehicle such as an automobile and like vehicles housed in the testing chamber an atmospheric pressure of which is kept low.
2. Description of the Prior Art
A performance and durability test of the automobile, in which test an automobile's drive in mountainous districts is simulated, is conducted in an environmental testing chamber an indoor-pressure of which is lower than the pressure of open air. In such a conventional low-atmospheric pressure environmental testing chamber is provided a pre-chamber which is a preliminary chamber for allowing an operator to get in/out of the testing chamber without being subjected to a drastic change of the atmospheric pressure.
However, in the conventional pre-chamber, a control of the air-pressure therein is difficult in operation. In other words, in the operation, a considerably high technique and a skill are required to make it impossible for an average operator to conduct such control of the air-pressure in the pre-chamber.